1. Field of the Invention

The present invention relates to an electronic sensor or sensor device, in particular an acceleration sensor, having a sensor housing in which a chip module is mounted, the sensor housing having plug contacts that are connected via electrical connections to terminals that are situated on a module housing of the chip module.

2. Description of Related Art

Such a sensor, in which the chip module is mounted immediately in the sensor housing without a substrate or circuit board, is known from published German patent document DE 10 2006 037 691 A1. Here, it is necessary to form press-in zones in the module housing itself and to form corresponding press-in pins on the sensor housing.

However, differing from the named generic prior art, the most widely distributed type of sensor manufacture is the assembly of an SMD-capable module housing (whose design is oriented towards a standard chip housing, e.g. SOP), containing the sensor chip, the ASIC (signal processing chip), and, if warranted, passive components, on a circuit board using standard SMD processes. The equipped circuit board is subsequently mounted, using binding processes or soldering processes or cold contacting technology (press-in technology, insulation-piercing clamps, etc.), in a previously manufactured plastic housing having metallic inserts. Finally, this sensor housing (the final housing of the sensor) is sealed with a roof (glued, laser-welded, etc.) or is cast with a filling material. Such a chip module provided for fastening on a substrate is known for example from DE 10 2004 058 815 A1. In these designs, a circuit board is accordingly required as a bearer of the module housing and of passive components that may be present. Today, this technology and the assembly processes associated therewith have a strong determining effect on the price and marketability of a sensor, with regard also to the forthcoming development/conversion of solder techniques to lead-free solders and the associated development costs.

In the area of the module housing, a large number of housings and “pin shapes” are known. In particular, dual in-line packages (DIP) are known as module housings, though not in their original shape having terminal pins provided for “plug-through assembly” in metallic circuit board bores, but rather having terminals designed for currently standard surface mounting technology (SMD).

With regard to the electrical sensor, the present invention provides that the module housing has terminal pins that protrude laterally outward, each pin tapering at its free end, and in that at least one metallic bearer strip is provided that is fashioned in a first end area as a plug contact and that has in a second end area for at least one terminal pin a respective spring-clamp contact point that forms a flexible press-in zone for the corresponding terminal pin. It is also the case according to the present invention that at least one opening is provided in the bearer strip for each of the terminal pins that are not to be contacted.

Thus, the present invention succeeds in achieving the reliable and mechanical integration of a module housing that can be produced and standardized using standard processes in a plastic housing that can be manufactured to order for the individual customer. According to the present invention, the use of lead in the sensor is not required. The present invention is based on an integrated sensor design based on a minimally modified standard dual in-line package (DIP) with completely integrated switching technology, mounted and further processed on a spring contact bearer using press-in technology. On the basis of this design, the present invention does without a circuit board or a substrate, resulting in a reduction in costs. A further positive effect on costs is achieved by the fact that according to the present invention no modification of the matrix of known DIP lead frames is required, so that production is possible using standard machines and tools. Due to the only slight modifications made to the pins of the DIP, measurement or compensation using standard measurement measures is enabled, so that no expensive special designs are required.

In addition, a particular advantage results from the variability provided by the present invention with regard to those terminal pins for which contacting is desired. For this purpose, only those pins are pressed in that are necessary for electrical functioning and mechanical stability. For all other terminal pins, corresponding openings are provided in the bearer strip.

According to an example embodiment of the present invention that is regarded as particularly advantageous, in order to form the press-in zones the bearer strip is stamped down in the second end area to a smaller thickness than in the first end area, and the press-in zones each have a slot situated transverse to the longitudinal direction of the bearer strip in order to accept the corresponding terminal pin, as well as two cross-struts, the cross-struts each being adjacent to one of the oppositely situated sides of the slot on the one hand and to a respective opening in the bearer strip on the other hand. Thus, the required flexibility of the press-in zones can be realized through simple stamping measures.

According to an advantageous development, the bearer strip can be designed, through the choice of its material, its thickness, and the situation and size of the slot and of the openings, in such a way that a spring action of the cross-struts is provided during the pressing in of the terminal pins.

As a module housing, a low-cost standard chip housing, in particular a dual in-line housing (DIP), can advantageously be used as long as it has terminal pins that are capable of plug-in assembly, or as long as such pins are produced, for example by straightening SMD-capable bent pins.

A method according to the present invention for producing a sensor or sensor device provides that the module housing is mounted on the metallic bearer strip or strips using press-in technique, and that the module housing and the bearer strip are subsequently embedded in a sensor housing by molding around them together with plastic.

FIGS. 1A, 1B and 1C show, from the front (FIG. 1A), in a top view (FIG. 1B), and from the side (FIG. 1C), a representation of a dual in-line package (DIP), standardized according to JEDEC, having in each case four pins 4 protruding from the two longitudinal edges. Module housing 1 of chip module 2 is manufactured in a known manner using a transfer molding process (material: an epoxy-based molding compound). Module housing 1 contains, on a structured lead frame (circuit bearer), the microstructured sensor chip, the ASIC, and passive components (none of which are shown). According to the present invention, the only modification is that the shape of terminal pins 4 (“small legs”) is slightly modified. The modification includes at least a tapering 3 at the free end of each pin 4. A stop surface 5 is also advantageous. Accordingly, in the depicted exemplary embodiment the basis of chip module 2 is a JEDEC-conformed standard module housing 1 having a dual-in-line design, in which the complete circuit, i.e. the circuit bearer (structured lead frame), sensor chip, ASIC, and passive components that may be present, are integrated. However, terminal pins 4 of this module housing 1 according to the present invention has been made narrower by a tapering 3 of the ends of the pins 4. Moreover, the transition from pin 4 to housing 1 is designed without a phase, differing from the original DIP. Rather, one stop surface 5 is provided per terminal pin 4.

The modification of pins 4 advantageously does not influence the raster dimension in the lead frame composite, in either the x or y direction. Normal separating bending tools may also be used. Thus, representation within known matrix lead frame structures is possible, as well as production on standard machines.

FIG. 2 shows the representation of the DIP module housing 1 shown in FIG. 1, in a composite of several module housings, in the form of a lead frame 6; more precisely, the Figure shows the excerpt of a matrix lead frame. Because this is very similar to a standard module housing 1, in which only the final shape of “pins” 4 has been slightly modified, manufacture is possible on standard machines using methods that are standardized worldwide, resulting in a significant cost savings, because existing manufacturing lines and existing injection molding and separating bending tools may be used.

FIG. 3 shows a representation of metallic bearer strip 7 according to the present invention, in two views. (In the top view, two bearer strips are shown next one another that are respectively responsible for the electrical and mechanical connection to terminal pins 4 situated on a common side of DIP module housing 1.) The thickness of bearer strip 7 is defined by the desired client interface; in this example, it is 0.6 mm thickness of plug contact 8. Raw band 14, made e.g. of CuSn₆ (cf. FIG. 4), is stamped down on one side (here in the left end area of bearer strip 7 shown in FIG. 3) to the thickness required for the contacting to DIP housing 1. The structure of clamp-spring contacts 9 for the later receiving of DIP housing 1 are stamped into stamped-down band 14, and are galvanically coated if warranted.

According to the present invention, metallic bearer strip 7 performs two functions:

On the one hand, it realizes the plug contact interface. On the other hand, it provides the possibility of electrically contacting DIP module housing 1 using press-in technology (cold contacting technology), and of securely fastening said housing mechanically.

The performance of the first function is ensured by corresponding stamping tools and by the suitable choice of the thickness of bearer strip 7. For the second function, spring contact clamp points 9 are provided. In principle, here the standard press-in technique is inverted: the pin is made massive and the press-in area is designed so as to be resilient, or to perform a clamping function. According to the present invention, the pins are the small legs 4 of DIP module housing 1, and press-in areas 9 are represented by a function-oriented design of bearer strip 7. For this purpose, bearer strip 7 is stamped down to the required dimension, and spring-clamp contact points 9 are realized in the required number by stamped-in slots 10. Here, slots 10 are limited by cross-struts 11 that are formed using openings 12 and 13.

FIG. 4 shows a representation of bearer strip 7 according to the present invention as a composite in a continuous band 14 (only a small segment of band 14 is shown). In the form of a band 14, band galvanic processes are possible, such as those that are also typically provided in the case of press-in contacts. The individuation of bearer elements 7 by a stamping process does not take place until final assembly. Because the stamping process takes place in a band 14, galvanically applied surfaces may also be provided partially on plug pins 8, i.e., differing from the rest of bearer 7, so that the areas of bearer strip 7 can be provided with surfaces fitting their respective functional environments.

FIG. 5 shows a representation of the design according to the present invention. DIP housing 1 is connected to bearer strip 7 using press-in technology (or cold contacting technology); for the precise sequence, see also the detailed view shown in FIG. 6. Optionally, lateral guides, realized by a bending process, can be provided on bearer strip 7 for the pre-fixing of DIP housing 1. As an example, an eight-pole module housing 1 is shown, so that four terminal pins 4 are allocated to each bearer strip 7. As can be seen, the two center terminal pins 4 of each row of terminals are not contacted in press-in zones 9, but rather extend freely, i.e. without electrical contact, for example through opening 13. The accompanying terminal pins 4 that are not to be contacted during normal operation of the sensor are required only in test operation.

In FIG. 6 it can be seen how, in a bearer strip 7 that is correspondingly designed constructively and with regard to its material, a spring-clamp action on pins 4 of DIP housing 4 arises at spring-clamp contact points 9 through the press-in process. First, DIP pin 4 is threaded into a slot 10 of bearer strip 7. As it is further pressed in, DIP pin 4 comes into contact with cross struts 11, and exerts a lateral force on these struts, in response to which the cross-struts can yield flexibly to some extent due to their construction, or due to openings 12 and 13. Finally, the respective terminal pin 4 is completely pressed in, and creates a secure electrical and mechanical connection to bearer strip 7.

During the equipping with components, according to FIGS. 5 and 6 tapered areas 3 of pins 4 are situated in slots 10 provided for this purpose in bearer strip 7, because the dimensions of pins 4 in tapered area 3 are slightly narrower than the width of slots 10. Through application of force, pins 4 are pressed into slots 10. The clamping action is achieved in that pins 4 are broader in the non-tapered area than are slots 10 in bearer 7. Bearer 7 must here permit a certain spring action of cross-struts 11, which is easily possible through a corresponding design on the basis of the available parameters.

In order to secure this electromechanical connection, an intermediate housing 15 is molded around bearer strip 7; see FIG. 7. For the mechanical fixing of pressed-in DIP housing 1 on bearer strip 7, and in order to decouple the stress during the subsequent injection-molding process of the surrounding sensor housing (final housing), the design according to FIG. 5 is molded around by a surrounding intermediate housing 15 made for example of a partly flexible material (silicone). In the selected views shown in FIG. 7, the shape given to intermediate housing 15 can be seen; this shape is shown only as an example. The injection-molding tool required for the production of intermediate housing 15 can be used as a basis for the press-in process in that “sliding elements” perform the function of supporting the coupling in of force; see FIG. 10 below. These “sliding elements” in the injection-molding tool can also simultaneously perform the function of the ejection of intermediate housing 15. Moreover, intermediate housing 15 is advantageous with regard to the decoupling of the stress during the molding around (which takes place at very high pressure, >500 bar) by the plastic of the sensor housing.

Finally, bearer strip 7 and intermediate housing 15 are molded around with a plastic in such a way that a final housing (sensor housing) 16 results that contains plug interface 8 a (see FIG. 8) and a fastening possibility 17.

FIG. 8 shows a representation of the final sensor housing 16 having the previously described design, in a plurality of views and in a “through-view.” The shape has been chosen as an example and is suitable in particular for an acceleration sensor in a motor vehicle. An assembly pin 18 can also be seen.

FIG. 9 shows further views of the final housing 16 of the sensor. In order to permit the fixing of intermediate housing 15 in the injection-molding tool of the final housing 16, in the depicted exemplary embodiment an “attachment having a central recess” 19 is provided on the upper side of intermediate housing 15. The counterpart thereto is situated in the injection-molding tool (not shown), and supports the precise positioning of intermediate housing 15 relative to final housing 16. The injection point of final housing 16 is selected in such a way (e.g. underneath the socket) that the injected plastic mass presses intermediate housing 15 precisely against this receiving surface 19.

FIGS. 10 through 12 show various stages of a possible process sequence during manufacture.

According to FIG. 10, first bearer elements 7 that have been stamped free are positioned over the lower injection-molding cavity 21 that is provided for the manufacture of intermediate housing 15. In cavity 21 there are situated sliding elements 20 that have been extended to the height of bearer strip 7.

Through a pick and place process, using vacuum suctioning unit 22 DIP housing 1 (see FIG. 11, left part) is positioned relative to bearer strip 7 and is equipped with components (threaded).

A press-in tool 23 (see FIG. 11, right part) presses housing 1 or DIP pins 4 into spring elements 9 of bearer strip 7. During the press-in process, “sliders” 20 in injection-molding tool 21 simultaneously form the “counter-support” for the pressure force applied from above.

Press-in tool 23 and sliders 20 required to accept the force are subsequently retracted (see FIG. 12, left part); upper injection-molding cavity 24 is then sealed by the injection-molding tool provided for the manufacture of intermediate housing 15 (see FIG. 12, right part).

After the injection of the compound and cooling, intermediate housing 15 is finished. Sliders 20 here simultaneously act as “ejectors” of intermediate housing 15 from lower injection-molding cavity 21.

Finally, surrounding final housing 16 is molded around, with the result shown in FIGS. 8 and 9, providing plug interface 8 a and screw or assembly possibility 17 and 18.

In conclusion, in the following some essential advantages of the present invention are summarized:

An ideal decoupling of stress between DIP module housing 1 and bearer strip 7 is enabled due to the length of the pins on DIP housing 1. This also results in a very small constructive size of the overall sensor. In particular, the assembly processes are greatly reduced. Because no thermal assembly or connection processes, such as welding, soldering, etc., are required, no thermal stress is placed on the DIP module housing by the connection technology used. Because the possible housing shapes are practically unlimited, in particular sensor housings suitable for use in motor vehicles may also be realized.

In addition, there results a mitigation of the so-called “particle problem” of electrically conductive particles. Contamination by solder balls, flux residue, powder residue during welding, adhesive residue during silver conductive gluing, etc., is not a problem due to the assembly according to the present invention.

Given the use of a transfer molding method (i.e., if final housing 16 is manufactured from a molding compound/epoxy), intermediate housing 15 can be omitted if warranted.

Using one and the same DIP module housing 1, for many types of sensor all the sensing directions can easily be realized merely by varying the position of the bearer strip (0°, 45°, 90° sensors, etc.).